This invention relates generally to earthmoving machines that include two mechanisms for controlling the speed of the machine.
Earthmoving machines such as motor graders and wheel loaders include many hand-operated controls to perform functions such positioning an implement or a blade in several orientations, articulating the frame of the machine, and adjusting other machine settings. In many of these earthmoving machines control of the speed of the machine is controlled by a throttle hand lever that acts through the hydraulic system of the machine to actuate an engine speed actuator.
Current earthmoving machines require numerous hand controls because typically each hand control is used to control only one or two functions. Often, the operator of the machine must steer the machine and control its speed while performing many other functions, such as adjusting the blade tip, adjusting the blade angle relative to the frame, adjusting other implements, and adjusting the articulation of the machine frame. Performing all of these functions using the hand controls while controlling the speed using a throttle hand lever is difficult, inefficient, and fatiguing for the operator. To reduce difficulty, increase efficiency, and reduce operator fatigue, it is desirable to provide a dual function throttle control system that permits an operator to control the speed of a machine without requiring the operator to release the hand controls that control machine implements.
Training a new operator to operate a motor grader requires a great deal of time because of the complexity of motor graders. Frequently the operator will have first been trained to operate simpler earthmoving machines such as for example bulldozers. The typical bulldozer includes a decelerator in addition to a throttle hand lever. Thus, it is also desirable to provide a dual function throttle control including a decelerator that can be used in a motor grader to simplify training of motor grader operators.